The standard thickness of sheet metal depends on the gauge and the type of metal. For example, 3-gauge steel is 0.2391 inches thick, while a sheet of 3-gauge zinc is 0.006 inches thick.
The gauge of aluminum sheet metal begins at 6, and is 0.162 inches thick, while a sheet of stainless steel begins at 7-gauge and is 0.1875 inches thick. Galvanized steel begins at 8-gauge and is 0.1681 inches thick. However, an 8-gauge sheet of steel is 0.1644 inches thick, an 8-gauge sheet of stainless steel is 0.1719 inches thick, an 8-gauge sheet of aluminum is 0.1285 inches thick, and a sheet of 8-gauge zinc is 0.016 inches thick.